5.3 Budding Atlas of Bacterial and Archaeal Cell Structure Home
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Lifecycle

Hyphomonas neptunium grow a single stalk from one end of their cell body, similar to the Caulobacter crescentus you saw in Chapter 3. The function of the stalk, though, is different in this budding bacterium than in C. crescentus, which divides by more conventional fission.

H. neptunium have evolved a program of stages they pass through in the course of their life. When a newborn cell is released, it is in the “swarmer” stage, using a flagellum (discussed in the next chapter) to swim away in search of a favorable location to settle down, jettisoning its flagellum and growing a stalk like this with which to make its own bud. Once a cell settles down into the “stalked” stage, it spends the rest of its life sending off buds as long as conditions are good. We will discuss this lifecycle, and its advantages, more in Chapter 8.4.

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Budding

What if your cell divides a different way? Some bacteria produce daughters not by fission, but by budding, like this Hyphomonas neptunium cell. These cells concentrate their growth at the end of a stalk (⇩), producing a daughter cell like blowing a bubble. When the bud becomes big enough, they divide at the end of the stalk to release it. First, though, they have to make sure all the necessary components make it into the bud. The process is most dramatic for the genome; here you can see a copy being transferred through the stalk. The chromosome here resembles a double-stranded DNA helix, but it is actually a higher-order structure of supercoiled DNA. (We think the crossbands are proteins that help pack the DNA, not hydrogen-bonded bases.)

Several other bacterial species divide by budding, although not all have stalks. Some simply bud from the main cell body; you will see an example later in this chapter.

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